Measurement of the Frictional Properties of Wool Fibers

The surface of a wool fiber consists of a series of overlapping scales so arranged that when the fiber is rubbed from the tip towards the root it is considerably rougher than when it is rubbed in the reverse direction. Accordingly, when a material containing wool fibers is sub mitted to mechanical action such as occurs in laundering or in fulling processes the fibers tend to migrate in the direction of their roots. This migration tendency is recognized as one of the principal factors in the formation of the entangled mass known as a felt, and in the excessive shrinkage which wool materials exhibit during laundering. An instrument for measuring these surface frictional properties on individual fibers is described. Measurements made on many wool fibers indicate large variations in frictional properties. The relationship between friction and diameter was studied and no significant correlation was found. Measurements made in the dry state resulted in all cases in lower values than measurements made on the same fibers in the wet state. The coefficients of friction of a few varieties of wool and of human hair and mohair are described.